Polyunsaturated xcfx89-3 and xcfx89-6 fatty acids, such as xcex1-linoleic acid and linoleic acid, are among the fatty acids essential to mammals and human beings. Besides linoleic acid, other isomeric octadecadienoic acids occur in nature. They are distinguished by conjugated double bonds at carbon atoms 9 and 11, 10 and 12 and 11 and 13. These isomeric octadecadienoic acids are collectively referred to in the scientific literature as conjugated linoleic acids (abbreviation: CLAs) and have recently attracted increasing attention (NUTRITION, Vol. 19, No. 6, 1995).
Various working groups have reported on the significance of CLAs to the organism. Recently, Shultz et al. reported on the inhibiting effect on the in-vitro growth of human cancer cells (Carcinogenesis 8, 1881-1887 (1987) and Cancer Lett. 63, 125-133 (1992)). In addition, CLAs have a strong antioxidative effect so that, for example, the peroxidation of lipids can be inhibited (Atherosclerosis 108, 19-25 (1994)).
The use of conjugated linoleic acid in animal feeds and, in this connection, also in human nutrition is known, for example, from WO 96/06605. EP 0 579 901 B relates to the use of conjugated linoleic acid for avoiding loss of weight or for reducing increases in weight or anorexia caused by immunostimulation in human beings or animals. WO 94/16690 is concerned with improving the efficiency of food utilization in animals by administering an effective quantity of conjugated linoleic acid.
CLA is obtained by so-called conjugation of intermediate products containing linoleic acid, i.e. products containing a carboxylic acid function with 18 carbon atoms and 2 double bonds in the 9- and 12-position which are both present in the cis-configuration. It is important during the conjugation reaction to ensure that only the two CLA main isomers (9cis, 11trans and 10trans, 12cis), of which the effect is described in the literature cited above, are formed. An isomer mixture like the CLA used for industrial purposes, for example in paint manufacture (for example Edenor(copyright) UKD 6010, a product of Cognis, Dxc3xcsseldorf), is not wanted.
Pure CLA is often obtained by saponification of oils containing linoleic acid [WO 96/06605, EP 0 902 082 A1]. The disadvantage of these processes lies in the high level of unwanted isomers. These unwanted isomers can be separated by enzymatic esterification, as described in WO 97/18320. In order better to control the isomer content, the corresponding esters may also be used as intermediates. It is known that the corresponding esters can be produced by esterification of the fatty acids with methanol or ethanol. According to the literature, the methyl and ethyl esters of linoleic acid are particularly suitable starting materials for gentle conjugation [WO 99/47135]. There is no known reference to the particular suitability of any of the methods for producing methyl or ethyl linoleate in high purity with regard to the 9cis, 12cis-configuration. WO 99/47135 describes a process for the production of conjugated linoleic acid by esterification or transesterification under nonaqueous conditions in which the alkyl ester obtained is subsequently isomerized in another step.
Another problem in the production of CLA or CLA intermediates is that, hitherto, the necessary reduction in the C16 content and the simultaneous increase in the C18:2 content could not be achieved without fractional distillation in a column for the total quantity of crude ester. Instead, only part of the reactor contents is fractionated towards the end of distillation of the main fraction, with the result that the yields are unsatisfactory.
The problem addressed by the present invention was to provide raw materials for the production of conjugated linoleic acid (CLA), such as methyl or ethyl linoleate for example, from intermediate products rich in linoleic acid, with the provisos that  the C16 content would be reduced and the C18:2 content simultaneously increased,  9cis, 12cis configuration would remain intact to a high degree and  no uncontrolled pre-conjugations or isomerizations would occur during production of CLA raw material,  the process would be economical, i.e. could be carried out with high yields on an industrial scale.
The present invention relates, in general, to food supplements and, more particularly, to a process for the production of raw materials for the production of conjugated linoleic acid.
The present invention relates to a process for the production of raw materials for the production of conjugated linoleic acid, characterized in that
(a) triglycerides containing at least 60% by weight of linoleic acid are transesterified with alcohols having a chain length of 1 to 4 carbon atoms at a temperature of 80 to 120xc2x0 C. and
(b) the transesterification mixture thus obtained is subjected to distillation.
To this end, a triglyceride rich in linoleic acid, for example sunflower oil, preferably safflower oil, more preferably refined safflower oil, is transesterified with methanol, preferably ethanol. By comparison with esterification with linoleic acid, it has surprisingly been found that almost no unwanted pre-conjugations and isomerizations occur. The transesterification takes place under gentle conditions, i.e. without the use of inert gas or ethylene or propylene glycol.
Transesterification
The fatty acid glycerides to be used as starting materials in accordance with the invention may be the usual natural vegetable or animal fats or oils. These include, for example, linola oil, sunflower oil and, preferably, safflower oil. The principal constituents of these fats and oils are glycerides of various types of fatty acids which contain considerable quantities of impurities, such as for example aldehyde compounds, phospholipid compounds and free fatty acids. These materials may be used either directly or after preliminary purification. They are fatty acid mixtures which contain at least 60%, preferably more than 70% and, more particularly, in excess of 75% by weight of conjugated linoleic acid. The reaction takes place under controlled conditions without the use of inert gas. The reaction is preferably carried out at a temperature in the range from 80 to 120xc2x0 C., more preferably at a temperature of 85 to 100xc2x0 C. and most preferably at a temperature of 88 to 95xc2x0 C. The glycerol formed during the reaction is continuously removed via a coalescence separator and approximately two thirds of the total quantity of catalyst is continuously added during the reaction. Suitable catalysts are alkali metal and/or alkaline earth metal alcoholates or hydroxides, more particularly sodium methanolate and/or sodium glycerate and, in a particularly preferred embodiment, sodium ethylate. The reaction takes place over 4 to 7 hours and preferably over 5 to 6 hours. In the final step of the transesterification, the reaction mixture is neutralized with citric acid. Taking the reaction products preferably used into account, the process is preferably used for the production of a safflorethyl ester with a small content of unwanted isomers.
Distillation
The object of distilling the transesterified reaction mixture is to remove glycerides, free glycerol and soaps. In addition, it leaves the reaction product with a more attractive color. In addition, depending on the raw material, the palmitic acid content can be reduced and the linoleic acid content increased by distillation of the product. Initially, the excess ethanol is distilled off after application of a vacuum of 100 to 300 mbar. Free glycerol additionally accumulating during distillation of the ethanol is removed via the separator. Thereafter, the temperature is increased to 150-200xc2x0 C. and preferably to 160-180xc2x0 C. under a vacuum of 1 to 3 mbar. 5 to 10% of the first runnings are removed and the product is distilled to a residue of 5 to 10%. In order to obtain a high yield, fractional distillation may preferably be applied. In addition, in order simultaneously to reduce the C16 content and increase the C18:2 content, it has proved to be of advantage either to carry out a batch distillation from a reactor surmounted by a column, which increases the C16 content in the first runnings distillate, or to carry out distillation in two stages, in which case around 5 to 10% by volume of the first runnings is removed from the fractionating column and the main fraction is distilled via the column head. With the second alternative in particular, the C16 content in the main fraction can be reduced from a starting value of 6.5% by weight to 0.7% by weight, the C18:2 content simultaneously increasing from 75.5% by weight to 81.4% by weight.
Conjugated Linoleic Acid (CLA)
In the context of the invention, conjugated linoleic acid is preferably understood to include the main isomers 9cis, 11trans octadecadienoic acid and 10trans, 12cis and the isomer mixtures which normally accumulate in the production of conjugated linoleic acid. The raw materials produced by the process according to the invention should already contain a high percentage of the preferred isomers.
Commercial Applications.
The process according to the invention is intended for the production of raw materials for the production of conjugated linoleic acid (CLA). The small percentage of unwanted isomers in the crude product saves further isomer separation and purification steps in the production of the CLA. The CLA produced from the raw materials may be used for all the applications already known from the literature for conjugated linoleic acid, for example in foods, preferably so-called functional foods, and in pharmaceuticals, particularly as a supporting agent in the treatment of tumours or even for the treatment of people suffering from catabolic conditions.